The invention relates to a method for the stabilization of ammonium nitrate in reference to storage behavior, to thermal stability vis-a-vis modification changes and to the mechanical strength by adding polyphosphates, in particular ammonium, to practically water-free melts or aqueous solutions to be evaporated accordingly.
It is known that one can add Kurrol's salt in amounts of more than 10% by weight to the ammonium nitrate for stabilization. Also magnesium nitrate and other magnesium salts as well as potassium nitrate have been used for this purpose.
Furthermore, fertilizers to which up to 2.5% boric acid or its salts had been added as stabilizers, have been improved further by adding a few tenth percent ammonium sulfate or diammonium phosphate.
Granular ammonium nitrate has been coated or powdered with these or similar substances in a very finely broken up form. In this manner, 0.1 - 2% sodium phosphate, sodium pyrophosphate or sodium polyphosphate, among others, have been used. The disadvantage of this method consists in that additional apparatus is needed for the application of the coatings and that this step in the process prolongs the production time. Furthermore, powder layers of this type have a tendency to separate, the goods become inhomogeneous, and an undesirable dust formation develops easily during the handling of such products during transport, when loading or unloading and during dispersing.
The first mentioned methods require the use of relatively large and in some cases also relatively expensive products or they bring about rather cumbersome methods during preparation, e.g. the proportion of mixtures has to be adhered to exactly.